Nuclear transplantation of embryonic stem cells in mice

The developmental ability of enucleated mouse eggs that had received embryonic stem cells was examined. In a preliminary study, none of the reconstituted eggs formed a nucleus using inactivated Sendai virus (HVJ) after activation with ethanol. DC pulses were applied at 100 or 140 V mm-1 in addition to this treatment. After electrofusion, 29-40% of reconstituted eggs formed nuclei and 41-60%, 25-44%, 12-24% and 12-18% developed to two-cell and four-cell and morulae and blastocysts, respectively. The ability of reconstituted eggs to form blastocysts did not depend on the age of recipient eggs, except in cases of very young and very old eggs. Although implantation sites were observed, no live fetuses were obtained after the transfer of reconstituted eggs to the recipients.